Each year, more than four billion tons of hazardous products and waste are transported throughout the United States. The safe handling and carriage of these materials (which include explosives, flammables, corrosive or toxic chemicals, poisons, spent reactor fuel and low-level waste, and disease-causing biological agents) are of major concern to federal, state and local agencies.
These hazardous materials move by land, sea and air modes of transportation at a rate of about 500 shipments per day. The types of vehicles carrying hazardous materials on the nation's highways range from tank trunks, bulk cargo carriers and other specially designated mobile containers, conventional tractor-trailers and flatbeds which carry packages, cylinders, drums and other small containers.
Trucks carry more hazardous materials than any other mode of transportation. Trucks travel on public rights-of-way through every jurisdiction, mingling with other traffic and thus increasing spill and accident risks.
Movements of gasoline and petroleum products (by far the most frequently transported hazardous materials) account for more hazardous materials transportation accidents, injuries and damage than transport of any other classified commodity. It is the risk of death or injury that causes the deepest concern. Hazardous material accidents are often spectacular, causing environmental contamination, injury and loss of life. No state or local official can erase the memory of an overturned load of explosives or tank of chemicals in an area for which he/she is responsible.
These experiences and the almost daily news reports of a hazardous material spill somewhere in the world have fueled the demand for strong enforcement of mandatory safety measures, improved emergency response and improved pre-accident safety technology onboard the vehicle to new heights of industry awareness. The insurance industry, the U.S. Department of Transportation, and state and local regulatory agencies have begun mandating safety in all facets of the trucking industry. The liability insurance for carriers, for example, has increased dramatically recently (over 500% within a year in some cases) and the rates are expected to continue to increase with no end in sight. In addition, the EPA (Environmental Protection Agency) has gained increased muscle from Congress and now has the ability to levy stiff fines after a major or minor spill has occurred. EPA action may result in fines of tens of thousands of dollars being levied on the individual carriers for cleanup operations.
There is no doubt that driver error and impaired operating ability is the single largest cause of truck accidents today. Driver training and awareness have therefore been targeted as the primary issue to all parties concerned. Safety and maintenance programs in the trucking fleets have been and will continue to be under close scrutiny by the insurance companies providing coverage. The slightest infraction or inappropriately filled-out supporting documentation may often result in immediate cancellation by the insurer. The serious carriers have complied and have diverted more money and time to proper driver training and safety maintenance programs for existing equipment. Such maintenance programs extend to brake systems, tires, steerings, lighting and overfill prevention systems.
In view of the increased costs to society of accidents in the trucking industry and the great public concern that presently exists over truck safety, it is obvious that any steps that could be taken to increase truck safety would be highly valuable. Truck manufacturers have taken steps to increase the safety of their products. For example, new "anti-skid" type braking systems have been designed and are now being installed in new trucks in order to minimize jackknifing and other dangerous results of careless or unskilled driver braking techniques. Other safety equipment (e.g., automatic fail-safe manhole covers for tank trucks, impact and explosive resistant tank shells and associated equipment, etc.) are now or soon will be mandated by federal rule. Insurers and governmental agencies are now mandating better driver training and education so as to increase the skill and competency of the nation's truck drivers and thus reduce the number of accidents on the road.
We all realize, however, that even the most careful and skilled drivers operating properly maintained and equipped trucks may still have accidents. One common cause of accidents is loss of traction on icy or wet road surfaces before the driver realizes a problem exists. Hydroplaning can occur without warning, causing even brand new tires to lose traction. Loss of front wheel traction due to hydroplaning or ice at the time the driver attempts to steer the truck around the curve can result in a catastrophic accident. Unfortunately, in many cases, the drive is not even aware that he has lost traction until he begins to lose control of the truck.
Load shifting and other rear instability problems are another very serious hazardous condition which can occur without warning and may very adversely affect the driver's control over his truck. Good drivers take great care to secure their loads to prevent them from shifting during transit. Unfortunately, knots can come untied, ropes or chains can break and anchor points can become loosened. Careful checking of the load at rest and fuel stops reduces but does not eliminate the problem. Overloaded or improperly loaded vehicles are subject to turning over if driven at excessive speeds around curves.
Needless to say, an automatic system capable of alerting the driver in advance that a hazardous or potentially hazardous condition (e.g., loss of front wheel traction and/or serious load imbalance) has occurred would increase safety. Such useful and timely warnings would be extremely valuable in helping to avoid accidents--and would be useful not only for inexperienced or inattentive drivers but also for the most experienced and careful of drivers.
In accordance with one aspect of the present invention, front wheel rotation and rear truck frame loading are both monitored. Specifically, in the preferred embodiment, the time it takes for each of the two front (steering) wheels to rotate is monitored independently, and these two rotation intervals are compared to determined whether one front wheel is slipping with respect to the other. A warning indication is provided if significant front wheel "desynchronization" is detected.
In accordance with another aspect of the preferred embodiment of the present invention, the downward forces exerted by the truck load on left and right rear truck frame are measured periodically and compared. In the preferred embodiment, deflection of left rear and right rear independent truck suspension frame members is used as an indication of the loading of those frame members, and load is measured using strain gauges integrally installed within those frame members. The ratio of left rear to right rear loading is calculated periodically (in the preferred embodiment, a "pseudo-sliding window" averaging method is used to filter the loading data so as to provide noise rejection). A warning indication is provided if the calculated ratio indicates uneven rear truck loading (e.g., as might be caused by shifting of the load or other factors).
A highly useful audio visual user interface is also provided. In the preferred embodiment, this user interface includes four illuminating lamps and a speaker audio output. This interface is relatively unobtrusive when no hazardous conditions are detected, but virtually instantaneously alerts the driver whenever a hazardous or potentially hazardous condition arises.
A "low speed" operation is provided which reliably detects when the truck is moving at a relatively low speed and disables, in the preferred embodiment, the front wheel synchronization monitoring/alarm operation during such low speed operation.
Other features and advantages of the present invention include the following:
helps the truck driver to drive more safely; PA1 helps to protect the vehicle; notifies driver if he/she has broken a leaf spring; PA1 helps reduce risk of accident and most importantly, could possibly save lives; PA1 utilizes state-of-the-art microprocessor based technology to provide higher reliability and extra performance; PA1 includes an advanced switching power supply allowing the system to operate on 12-24 volts, positive or negative ground electrical systems without modification; PA1 utilizes the latest low power CMOS circuit technology to reduce power and enhance reliability under all operating conditions; PA1 sensor and associated circuitry offer high performance and immunity to external factors even in the worst operating conditions; PA1 provides a rear loading alarm which is useful in warning the driver of excessive speed on curves and when the trailer rear end is reaching the possibility of sliding sideways or overturning; PA1 reliably and instantly detects when the truck is hydroplaning on a wet road or is losing steering ability on an icy road surface; PA1 preferred embodiment does not control the truck in any manner but instead has the function of alerting driver and providing him more time to react as his truck approaches an unsafe condition caused by trailer instability, a flat tire or tractor hydroplaning; PA1 literally teaches the driver to drive more safely by providing him with more information he can use to make critical decisions with (decisions that could save property, money and most importantly, lives); PA1 uses a windowing technique to reject false front wheel pulses and thereby discriminate between actual front wheel pulses and pulses attributed to noisy environment; PA1 provides a low speed mode in which synchronization data from front wheels is ignored to allow for low speed maneuvering; PA1 requires several successive front wheel interval measurements to be under the threshold before leaving the low speed mode and entering the active wheel synchronization mode in order to reject noise during low speed mode and prevent false alarms; PA1 includes an advanced "pseudo-sliding window" technique to filter the rear load data, thus smoothing the data and eliminating sensitivity to noise sources; PA1 provides variable gain load amplifiers, allowing the installer to compensate for variations in truck geometry, weight, sensor location and the like; PA1 includes an automatic DC level setting circuit which eliminates the need for DC offset adjustments; PA1 load cell amplifiers located in proximity to the load cells at the rear of the truck include a DC balance feature to null out signals with no load in the truck; and PA1 automatic silence feature silences the alarm if it persists for more than an acceptable amount of time (thus eliminating the need to disconnect the unit or turn off power when a sensor or a system component failure causes a continuous false alarm).